Modified lubricating oil



Patented Mar. 28, 1950 MODIFIED LUBBICATING OIL Richard W. Mertes, Los Angeles, Calii., assignor to Union Oil Company of California, Los Angelcs, Calif., a corporation of California No Drawing. Application October 14, 1946, Serial No. 703,097

30 Claims. (Cl. 252-33) This invention relates to lubricating oils and is a continuation in part of my co-pending application, Serial No. 458,459, filed September 15, 1942 (now abandoned).

Primarily, the object of the invention is to produce mineral lubricating oils for internal combustion engines which possess a very high degree of detergent power for the removal of resinous and similar deposits from the piston skirts, piston rings and ring grooves of internal combustion engines.

In many internal combustion engines, especially Diesel engines, where severe service conditions are encountered, there is a stronger tendency than ordinarily to deposit on the piston skirts and upon the rings and in the ring grooves an objectionable amount of resinous and varnishlike materials. The deposition of these materials may be controlled and largely prevented, and to some extent may be removed after formation, by the use of certain types of additives in the lubricating 011.

One form of additive which possesses some merit is metal soaps of oil-soluble petroleum sulfonic acids obtained by the sulfonation of mineral oil fractions, such as mineral lubricating oil fractions. The particular sulfonic acids employed are the so-called mahogany acids, that is, the oil-soluble sulfonic acids produced in the process as distinguished from the water-soluble, socalled green acids, although it is possible sometimes to use a mixture of both the mahogany acids and green acids because of the fact that mahogany acid soaps possess some solubilizlng properties for the green acid soaps when added to mineral lubricating oil. These sulfonic acids are produced according to well known processes by treating the oils with strong or fuming sulfuric acid or chlor-sulfonic acid. The green acids are separated in the sludge, and the mahogany acids may be recovered as soaps by in-v troducing the desired base material, for example, lime or calcium hydroxide to produce the corresponding metal soap in the treated oil. Or, where the mixed soaps are desired, the whole batch may be treated with the desired base material. Or, the sodium soap may be recovered by any well known or preferred method and a desired soap prepared therefrom in any known manner and combined with oil to yield a suitable concentrate of the metal sulfonate in a petroleum oil fraction.

In preparing the final lubricating oil, the desired sulfonate, or a concentrate thereof, is added to the oil and dissolved therein by the simple expedient of admixture and agitation, to pro- .of soap in the final oil is ordinarily in the neighborhood of 1% to 2% but may vary from about 0.5% to 3% or more as desired or required.

The particular improvement of this invention resides in further treating the recovered sulfonate or sulfonate concentrate, with a base for the purpose of increasing the detergent properties of the soap. I have found that the soap or soap concentrate may have additional base combined therewith by a more or less simple mixing and heating operation followed by filtering. It is not clear whether the result is a loom complex formed by the sulfonate and the base, or whether the sulfonate serves as. a solubilizing agent to hold the base material in solution in the 011. Since its oil solution exhibits the Tyndall effect and since the number of moles of base per mole of sulfonate can be made larger than would normally be expected for any new type oi complex other than a loose addition compound, the sulfonate very likely holds the base in solution in the form of a colloidal suspension. In addition to improving the detergent properties of the oil, the inclusion of the base in the sulfonate imparts the further characteristic of increasing what has been called the alkaline reserve" of the oil. Soaps of this type in oils serve to neutralize acidity which is formed in the oil during use or in some manner to counteract the development of corrosive conditions formed in the oil during use which are detrimental to bearings sensitive to such conditions. Apparently, when these soaps are acted upon by liberated acids in the oil, the strong acids so liberated are neutralized.

In preparing the improved oil of this invention a solution or slurry of the desired base is added slowly at somewhat elevated temperatures and with stirring to the desired oil-soluble metal sulfonate. The sulfonate is preferably in solution in oil in the form of a concentrate. The temperature to which the mixture is heated during the addition of base is preferably between about 200 F. and about 450 F., although it is possible to produce the desired result at lower temperatures such as about '150 1'. or at even higher temperatures such as about 500 I". As set forth in said application a preferred range of 60 temperatures is from about 350 F. to 450 1". It

515 removal of water and insure dehydration. Following the mixing and dehydration which may take place, for example, within about one hour. the product is filtered to remove unreacted base or other material which has not been solubilized during the treatment.

In preparing a sodium hydroxide-calcium sulfonate complex, 'a 500 B. solution of sodium hydroxide is introduced dropwise into a small batch of calcium sulfonate concentrate. During the addition, the mass is heated to 200 F. and continuously stirred. Vacuum may be applied during the addition of the hydroxide or after the addition is complete to efi'ect dehydration. The product is then filtered.

In preparing lead oxide-calcium sulfonate concentrate, an aqueous slurry of lead oxide is added slowly to a calcium sulfonate concentrate. The mixture is maintained at a temperature of about 200 F. and agitated during this addition. The batch is dehydrated with vacuum at a temperature of 200 F. as above indicated and the dehydrated product is filtered.

In some cases it is desirable to prepare the sulfonate-base complex at higher temperatures in order to eliminate the necessity for carrying out the dehydration under reduced pressure thus a sodium hydroxide-calcium sulfonate complex may be prepared byheating a calcium sulfonate concentrate to about 300 F. and adding a 50 B. solution of sodium hydroxide dropwise to the concentrate. The temperature is then increased to about 450 F. to insure rapid and complete dehydration.

The preparation of the corresponding carbonates may be carried out in the .manner described for the hydroxides and oxides or the carbonatesulfonate complex may be prepared by treating the hydroxide-sulfonate complexes or the oxidesulfonate complexes with carbon dioxide. Particularly in the case of the alkali metal complexes, they may be converted into the bicarbonatesulfonate complexes by continued treatment with carbon dioxide. Thus a sodium hydroxide-calcium sulionate product may be converted into the sodium carbonate-calcium sulfonate complex, or the corresponding bicarbonate complex, by blowing the hydroxide complex with carbon dioxide at elevated temperatures, such as about 200 F. or above or at temperatures indicated for the formation of the complexes. The carbonate and bicarbonate complexes may have particular value where the more highly basic character of the hydroxide-sulfonate complex might be objectionable. The carbonate and bicarbonate complexes, although having the same total alkaline reserve, are not as strongly basic in character as the hydroxide complex.

The above described operation results in a concentrate containing the desired modified sulfonate. .Any of the metal hydroxides capable of producing soaps suitable for this purpose may be employed instead of sodium hydroxide, for example, calcium hydroxide. Also, it may be feasible to introduce lime.

Another and very desirable form of the invention resides in combining the corresponding carbonates with the sulionate, for example, sodium carbonate or sodium bicarbonate. This has been accomplished in one manner by first treating with sodium hydroxide and then passing carbon dioxide gas through the resultant concentrate until the desired carbonate has resulted from the sodium hydroxide portion of the modified sulfonate.

In adding the base constituent to the soap, it has been found that the base can be introduced into the soap, or solubilized in the oil, as the case may be, until the amount of base taken up approximates 5% to 45% of the original sulfonate. Apparently, 45% is normally more than is necessary, and perhaps more than is desired, but it appears that up to about 20% of base figured on the sulfonate content is desirable. Normally, the content may be figured on the final oil to be produced. Thus, in the final oil the proportion of base may vary from 0.05% to about 0.5%. Commonly, it is desirable apparently to employ about 0.2% or 0.3% of base in the final oil.

In employing the modified sulionate in the oil, this ordinarily is done in the order of from about 1% to about 1.5%, although larger proportions may be used up to about 3% with correspondingly beneficial results, and larger proportions also may be used but without any apparent increased benefit. On the lower side, benefits are obtainable down to as low as 0.5% and 01. course correspondingly lower benefits are obtained with still lower proportions, e. g. 0.2% of the modified sulfonate.

In addition to employing sodium and calcium materials as constituents of the base, it is also feasible to employ the other alkaline earth metals such as magnesium, strontium and barium. These as well as other alkali metals such as lithium and potassium impart a desirable alkaline characteristic. It may also be in order to employ other metals such as boron, tin, aluminum, zinc, lead and the like. Besides using base materials of the type indicated, neutral salts which become properly solubilized may offer suitable detergent characteristics, and to this extent might be substituted for the bases. Similarly, other salts which are properly solubilized may ofier adequate detergent properties at least for some purposes. Such salts may be phosphates, acid phosphates, borates, and the like.

Although mineral lubricating oils containing the modified sulfonate of this invention are particu arly valuable lubricating oils, it is sometimes desirable to include one or more other detergents and/or one or more anti-corrosion agents in the final lubricating oil composition along with the modified sulfonate.

Anti-corrosion agents Anti-corrosion a ents which may be added to cooperate in maintaining proper anti-corrosion conditions, particularly in engines containin highly corrosion sensitive bearings, include all of the various types of anti-corrosion agents well known in the art. Oil-soluble metal salts of the acidic reaction products obtained by reacting phosphorus pentasulfide, or in some instances, phosphorus pentoxide. with an alcohol are particularly desirable anti-corrosion agents. The preferred reaction products are those obtained with phosphorus pentasulfide and these products may pe referred to as organic substituted thiophosphates.

The alcohols which may be employed in the preparation of desirable thiophosphates include the aliphatic alcohols such as butyl, amyl, isoamyl, hexyl, and heptyl, octyl alcohol, lauryl alcohol, cetyl alcohol and the like. These alcohols may be modified by the inclusion of phenyl and kindred aromatic groups forming alkaryl or aralkyl substituted alcohols. Also cyclo aliphatic alcohols such as cyclopentanol, cyclohexanol, cycloheptanol or the alkyl substituted cyclo aliphatic alcohols in which the alkyl substituent contains less thanabout 10 carbon atoms and preferably about or less carbon atoms may be employed. Thus the substituent groups will include preferably the methyl, ethyl, propyl, and amyl radicals and the methyl, ethyl, propyl, and amyl cyclohexanols are the preferred alcohols of this class. Other alcohols which may be employed are those containing an aromatic nucleus such as benzyl alcohol. Also in some instances phenols may be employed in place of the alcohol giving aryl substituted thiophosphates as for example phenyl substituted thiophosphates or methylphenyl substituted thiophosphates. In reacting an alcohol with phosphorus pentasulfide, which reaction may be effected for example by heating the mixture at 200 F. to 250 F. for about four hours, the reaction product consists of a mixture of acid thiophosphate esters, such as may be represented by the following formulas in which R is the hydrocarbon radical derived from the alcohol and R is hydrogen or R:

Other possible acid esters which may be present are the following:

The reaction products may be converted into the corresponding metal salts by direct reaction with a basic compound of the desired metal or by first neutralizing'with sodium hydroxide to form the sodium salt and subsequently metathesizing the sodium salt with a salt of the desired metal. Thus the sodium salt may be reacted with zinc chloride to form the zinc salt of the reaction prodnot.

A typically desirable thiophosphate was prean excess of either powdered metal or powdered metallic oxide, for example, powdered zinc or zinc oxide, until no more dissolves, as by standing over night at 250 F. Usually it is deemed preferable to use the metallic oxide. The resultant metal octyl thiophosphate, for example, the zinc salt, is readily taken up in mineral oil solution, employing either parafiinic or naphthenic type oil. The mere introduction of the salt into the oil with mild agitation and limited heating is suflicient to produce an oil solution to yield a concentrate, which in turn readily disperses in the final oil product to which it is added.

One particular material made in this manner analyzed 18.1% sulfur and 9.3% phosphorus, indicating the dioctyl thiophosphate as the principal constituent of the product with the probable formula:

Apparently the mono-'octyl thiophosphate also is present with the probable formula:

' Quite likely other thiophosphate esters of the 6 types above indicated in connection with the cyclohexanol product are also present in greater or lesser proportions.

Another class of anti-corrosion agents includes those compounds which may be defined as oilsoluble metal salts or soaps of high molecular weight, non-carboxylic weak acids having ionization constants below'about 5 l0-. This class of compounds includes the oil-soluble metal salts of alkyl substituted phenol sulfides or alkylated phenolic thio ethers. It also includes the oilsoluble metal soaps or salts of thio phenols, alcohols, enols, oximes or sulfo-amides. These weak acid salts and soaps are described in the United States Patent No. 2,280,419 to Wilson.

Another class of anti-corrosion agents which may be employed includes the oil-soluble metal salts of phosphorus and sulfur containing reaction products of a sulfide of phosphorus and a hydrocarbon. These materials are obtained by reacting phosphorus pentasulfide with a hydrocarbon having a molecular weight greater than about and subsequently neutralizing the reaction product with a basic metal compound. A description of these materials and methods for their preparation are given in United States Patent No. 2,316,082 to Loane et al.

Still another type of anti-corrosion agent consists of the oil-soluble metal salts of phosphinic or phosphonic acids obtained by treating hydrocarbons with elementary phosphorus andsubse quently forming the matal salts of the reaction products. Such compounds are described in United States Patent No. 2,311,305 to Ritchey.

Oil soluble metal salts of the condensation products of alkyl substituted phenols and formaldehyde are anti-corrosion agents which may be employed in the lubricating oil composition of this invention. These compounds and methods for their preparation are described in United States Patent No. 2,250,188 to Wilson.

Supplemental detergents Supplemental detergents which may be included in the final lubricating oil together with the modified sulfonate of this invention or together with the modified sulfonate and one of the above described anti-corrosion agents include oil-soluble petroleum sulfonates, such as those described above for use in connection with the preparation of modified sulfonates as well as any of the well known detergents which are employed in lubricating oil compositions. These include the oilsoluble metal salts of rosin acids, such as abietic acid, hydrogenated rosin acids, and the like. The metal salts of rosin acids are described in United States Patent No. 2 233,203 to Flaxman and the soaps of hydrogenated rosin acids are described in United States Patent No. 2,280,338 to Merrill.

Other detergents which may be employed as supplemental detergents include the oil-soluble metal salts of synthetic organic acids produced by oxidizing hydrocarbons or hydrocarbon fractions, such as highly paraffinic lubricating oil fractions, paraffin wax, and the like. Preferably the acids will contain in excess of 10 hydrocarbon atoms per molecule. These compounds are described in United States Patent No. 2,270,620 to Bray.

Still other types of supplmental detergents include the oil-soluble metal salts of fatty acids,"

halogenated fatty acids and aryl substituted fatty acids, such as dichloro stearic acid, phenyl stearic acid, and the like.

Desirable metals to be employed in the preparation of the oil-soluble metal anti-corrosion agents and detergents include the alkaline earth metals,

' such as strontium, barium and calcium and the polyvalent metals zinc, aluminum, tin, copper. magnesium, iron, nickel, mercury and chromium.

. Also in some instances alkali metal salts or soaps may be employed, such as sodium, potassium and like compounds, particularly in those instances in which the alkali metal compounds are sufficiently oil-soluble.

The anti-corrosion agents may be employed in amounts ranging from about 0.1% to about 3.0%

of the final lubricating oil composition although Final lubricating oil compositions The following examples illustrate typical lubricating oil compositions which have highly desirable detergent, anti-corrosion and alkaline reserve characteristics.

To a solvent treated Western lubricating oil having a viscosity index of about 90 is added 1.3% of a sodium hydroxide-calcium sulfonate complex prepared as indicated herein. The modified sulfonate is readily incorporated in the oil by simple mixing operations. The resulting oil has very good detergent and alkaline reserve characteristics. This product is a freely fluid oil possessing no appreciable viscosity increase beyond that of the mineral lubricating oil employed. Moreover, this oil has a detergent action which is improved up to a rating which might be called "most excellent as compared to a rating of rather poor" where a similar quantity of unmodified sulfonate is used. This 011 will remain free from insoluble oxidized products arising from oil deterioration much longer than the corresponding base oil or the base oil containing the usual unmodified sulfonates under service conditions.

Lubricating oil having unusually high detergent characteristics and anti-corrosion characteristics may be prepared by blending a mineral lubricating oil such as the solvent treated Western lubricating oil referred to above with 1.0% of a sodium hydroxide-calcium sulfonate complex and 0.5% of a zinc salt of the reaction product of octyl alcohol and phosphorus pentasulfide. This zinc salt may be referred to as a zinc dioctyl thiophosphate.

Another highly desirable lubricating oil composition may be prepared by adding to a lubricating oil, such as the one described above, 1.0% of a modified sulfonate such as lead oxide-calcium sulfonate complex and 0.7% of unmodified calcium sulfonate.

Still another highly desirable lubricating oil having exceptional detergent, anti-corrosion and alkaline reserve characteristics is prepared by incorporation in mineral lubricating oil 0.9% of a sodium hydroxide-calcium sulfonate complex 0.5% of an unmodified oil-soluble calcium sulfonate and 0.5% of zinc dioctyl thiophosphate.

The above examples of desirable lubricating oil compositions may be varied by varying the amounts and the types of modified sulfonates. the types of supplemental detergents and the 8 types of anti-corrosion agents without departing from the invention described herein.

The additives described may be employed in substantially any oil of the lubricating oil type. Normally the highly refined so-called highly parafflnic lubricating oils will be employed, however, naphthenic and other paraflinic lubricatinl oils are also usable.

It is sometimes desirable to prepare concentrates containing up to 20% or 30% of the modified sulionates alone or together with added supplemental detergents and/or anti-corrosion agents. Such concentrates are generally still fluid and do not set up like a grease. The concentrates are readily diluted by addition of lubricating oil to prepare the final lubricatim oil compositions.

Other improvements within the scope of the appended claims will occur to those skilled in the art.

I claim:

1. A mineral lubricating oil containing a minor but eifective proportion of about 0.2% to 3.0% of a complex formed by heating an oil-soluble metal petroleum sulfonate with an amount of an inorganic base selected from the group consisting of metal oxides, hydroxides, carbonates and bicarbonates together with mineral oil to a temperature of about 350 F. to 450 F., sufilcient to take up about 5% to 45% based on the sulfonate of the inorganic base in said complex, to solubilize said complex in the oil and dehydrate the product, said inorganic base having the function of enhancing the detergent capacity of the sulfonate.

2. An oil according to claim 1 in which the temperature is about 850 F.

8. An 011 according to claim 1 in which at least one of the metals is an alkaline earth metal.

4. An oil according to claim 1 in which at least one of the metals is barium.

5. An oil according to claim 1 in which the metal of the inorganic base is an alkaline earth metal.

6. An oil according to claim 1 in which the metal of the inorganic base is barium.

7. An oil according to claim 1 in which the inorganic base is a metal carbonate.

8. An oil according to claim 1 in which the metal base is a metal hydroxide.

9. An oil according to claim 1 in which the inorganic base is barium hydroxide.

10. An 011 according to claim 1 in which said composition contains between about 0.1% and about 3.0% of an oil-soluble metal suifonate as a supplemental detergent.

11. An oil according to claim 1 in which said composition contains between about 0.1% and about 3.0% of an anticorrosion agent selected from the group consisting of oil-soluble metal thiophosphates, oil-soluble metal salts of substituted phenols, oil-soluble metal salts of the condensation products of formaldehyde with an alkyl phenol and oil-soluble metal salts of a weak non-carboxylic organic acidic material having an ionization constant not exceeding about 5x10.

12. An oil according to claim 1 in which said composition contains between about 0.1% and 3.0% of an oil-soluble metal thiophosphate as an anticorrosion agent.

13. A mineral lubricating oil containing a minor but effective proportion of about 0.2% to 3.0% of a complex formed by heating an oilsoluble alkaline earth metal petroleum sulfonate 9 with an amount of an alkaline earth metal base selected from the group consisting of alkaline earth metal oxides, hydroxides, carbonates and bicarbonates together with mineral oil to a temperature of about 350 F. to 450 F., sufficient totake up about 5% to 45% based on the sulfonate of the alkaline earth metal base in said complex, to, solubilize said complex in the oil and dehydrate the product, said alkaline earth metal base having the function of enhancing the detergent capacity of the 'sulfonate.

14. An oil according to claim 13 in which the temperature is about 350 F.

1 tion products of formaldehyde with an alkyl phenol and oil-solublemetal salts of a weak noncarboxylic organic acidic material having an 15. An oil according to claim 13 in which said alkaline earth metal base is an alkaline earth metal hydroxide.

16. An oil according to claim 13 in which said alkaline earth metal base is an alkaline earth metal carbonate.

17. An oil according to claim 13 in which said composition contains between about 0.1% and 3.0% of an oil-soluble metal sulfonate as a supplemental detergent.

13. An oil according to claim 13 in which said composition *contains between about 0.1% and 3.0% of an anticorrosion agent selected from the group consisting of oil-soluble metal thiophos phates, oil-soluble metal salts or substituted phenols, oil-soluble metal salts of the condensation products of formaldehyde. with an alkgliphe- 1101 and oil-soluble metal salts of a weak non-carboxylic organic acidic material having an ionization constant not exceeding about 5x10-.

perature of about 350 F. to 450 F., suflicient to take up about 5% to 45% based on the sulionate of the barium hydroxide in said complex, to solubilize. said complex in the oil and dehydrate the product, said barium hydroxide having the functioniof enhancing the detergent capacity ionization constant not exceeding about 5x10-.

23. An oil according to claim 21 in which said composition contains between about 0.1% and 3.0% 01' an oil-soluble metal thiophosph'ate.

24. An 011 according to claim 21 in which said composition contains between about 0.1% and 3.0% of an oil-soluble metal salt of the condensation product of formaldehyde with an alkyl phenol.

25. An oil according to claim 1 in which the metal of the sulionate is diflerent from the metal of the base.

. 26. An 011 according to claim 25 in which one of the metals is lead.

27. An oil according to claim 25- in which one I of the metals is an alkali metal.

28. An oil according to claim Lin which the metal of the sulfonate is an alkaline earth metal and the metal of tne base is an alkali metal.

29. An oil according to claim 1 in which the sulfonate is calcium suli'onate and the base sodium hydroxide.

30. An oil according to claim 1 in which the sulfonate is calcium sulionate and the base is lead oxide.

RICHARD W. MERTES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PA'I'ENTS Number Name Date 1,871,942 Arveson Aug. 16, 1932 2,136,391 Miller Nov. 15, 1938 2,285,752 Van Ess June 9. 1942 2,322,307 Neely June 22, 1943 2,361,476 Higbee Oct. 31, 1944 2,369,632 Cook Feb. 13, 1945 2,372,411 Van Ess Mar. 27, 1945 2,409,726 Winning Oct. 22, 1946 2,413,311 Cohen Dec. 31, 1946, 2,418,894 McNab Apr. 15, 1947 2,444,970 Zimmer July is. 1948 

1. A MINERAL LUBRICATING OIL CONTAINING A MINOR BUT EFFECTIVE PROPORTION OF ABOUT 0.2% TO 3.0% OF A COMPLEX FORMED BY HEATING AN OIL-SOLUBLE METAL PETROLEUM SULFONATE WITH AN AMOUNT OF AN INORGANIC BASE SELECTED FROM THE GROUP CONSISTING OF METAL OXIDES, HYDROXIDES, CARBONATES AND BICARBONATES TOGETHER WITH MINERAL OIL AND A TEMPERATURE OF ABOUT 350*F. TO 450*F., SUFFICIENT TO TAKE UP ABOUT 5% TO 45% BASED ON THE SULFONATE OF THE INORGANIC BASE IN SAID COMPLEX, TO SOLUBILIZE SAID COMPLEX IN THE OIL AND DEHYDRATE THE PRODUCT, SAID INORGANIC BASE HAVING THE FUNCTION OF ENHANCING THE DETERGENT CAPACITY OF THE SULFONATE. 